Millions of patients take prescription drugs, over the counter (OTC) drugs, and dietary supplements. Driven by a variety of factors such as the desire to improve health, the convenience and relative low cost of self- medication, the assumption of natural products' safety, and the dissatisfaction with physician-prescribed treatments, many patients seek non-prescription drugs. When self-medicating, patients, like physicians, assess symptoms, evaluate options, and make decisions. Most patients would not willingly take medications that are known to be ineffective or harmful. Patients, however, do not always understand the indication, side effects, and contraindications of the products they take. Indeed, recent patient surveys found that the majority of potential drug-drug interactions involve non-prescription drugs. We argue that it is necessary to help patients make better-informed decisions regarding self-medication by proactively providing them with timely, relevant, comprehensible, and actionable information. The propose study will investigate what efficacy and safety information patients need and how to present that information to patients, develop a self-medication decision support tool to warn patients of potentially ineffective or harmful usage and suggest safer and more effective alternatives, and evaluate patient response to the decision support.